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More cycles or higher temp?

Which is more fuel efficient?  Setting the thermostat higher (66) and having the house warm to a higher temp and cool over a longer period OR set them thermostat lower (63) and have it cycle on more often. I have a 3 degree differential set on the thermostat.  I know the temps sound on the low side, but we get too warm if it's set much higher.

I have a one zone, 3,000 sq ft. house. and live in Mass. so the answer to this questions represents a good chunk of $$ in Jan-Feb-Mar for me.


  • fuel efficiency

    you don't specify your system or thermostat type, but in general, the greatest efficiency in any heating system comes from proper maintenance

    if furnace, check that filter!

    if steam, check that pressure, and maintain it in ounces! let the air out of the mains quickly, don't burn extra gas to squeeeeze it out. clean the dust out of, and check that burner for proper combustion! check that waterline for oily impurities, which need more fuel to make steam! make sure your thermostat is in the right location, adjusted for anticipation, rated for steam, and free from a cold draft, every time the front door is open!

    if hot water, clean that burner! oil the pump [but not too much!], and make sure your thermostat is set for hot water

    i'm not sure about the temperature differential, that you mention, but generally maintaining an even temperature, without too much setback is more economical. an accurate digital indoor/outdoor thermometer will tell you what your highest and lowest temperatures have been, in a couple of ares inside. that will tell you if you have even distribution of heat.--nbc
  • Devan
    Devan Member Posts: 138
    It depends

    on Outdoor conditions, and the thermal envelope of the building.


    If 0* outside and 66* inside than the rate of heat loss is greater than if 0* out and 63* inside. If it is 50* out, than the rate of heat loss is slower respectively .

    Type of windows and sq. ft of windows, insulation, thermal bridging, house orientation, all effect heat loss.

    Heat load is the number of btu's to replace heat loss. When boiler is on , the mass of the boiler , fluid, piping etc is being charged with btu's, gross input, the heat emitters (radiators, baseboard, floor heat) release some of those btu's into the room, net output.

    The real trick is to match energy in, with energy out, exergy, without wasting too much fuel and short cycling the boiler.

    Indoor and outdoor reset controls help a little, by lowering boiler supply temperature and longer cycles.

    In summary, depending on the thermal envelope, and rate of heat loss of the house, its more likely more efficient to keep boiler off longer, but when it does come on, to stay on longer.
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